Fluorescence resonance energy-transfer-based fluoride ion sensor.

The present work describes an energy-transfer-based fluoride sensor using the highly photo-stable Coumarin 540a (C540a)-Rhodamine 6g (Rh6g) dye pair. Rh6g exhibits a decrease in fluorescence emission, whereas C540a shows no change in response to fluoride. The increase in fluoride concentration decreases the energy transfer efficiency between the C540a donor and Rh6g acceptor in acetonitrile, leading to a subsequent recovery of fluorescence emission from C540a molecules. The sensing mechanism using fluorescence resonance energy transfer is found to be highly specific towards fluoride detection when compared to the response towards other anions. The fluorescence emission of both dyes is monitored to enable fluoride detection within a broad range.